PERIODONTAL TISSUE ANALYSIS WITH MECHANICAL IMPEDANCE MEASUREMENT

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The purpose of this project is to develop an index that indicates the dynamic and biological periodontal tissue changes during the orthodontic tooth movement without any invasion to the tissue. For this study, we chose a mechanical impedance measuring device and we made several improvements to adjust it for our purpose. Then, some clinical observations were carried out with this device as the means to know the conditions of tooth supporting structures, mainly the periodontal tissue. The following subjects were investigated.1. The reproducibility of the measurements of this measuring device, using normally erupted intact tooth.2. The change of the viscoelastic property of the normally erupted intact tooth during a day and during days.3. The relationship between the change of the viscoelastic property and the amount of the tooth movement during the orthodontic tooth movement.The reproducibility of the measurements of this device showed a good result. The coefficients of variations of the … More values of measurements were less than 10% (2.7%-8.2%). The viscoelastic property changes during a day of the intact tooth, which were measured nine times at one hour intervals showed slightly larger variations (7.2%-12.0%) comparing to the reproducibility of this device. The viscoelastic property changes during days were measured twice a week for four weeks. The coefficients of variations of the change during days values showed largest values (8.0%-17.1%) among these three.During orthodontic tooth movement, each tooth, even clinically normal canines, showed the different tissue reactions in the first four weeks, about the amount of the tooth movement and the viscoelastic property change. According to Reitan, The early stage of the orthodontic tooth movement could be divided into two periods. In the initial period, a tooth is moved by the compression of the periodontal fibers and in the secondary period, a tooth is moved by the bone resorption. Between these two periods, there is a hyalinized period in which the tooth stops its movement temporarily. In this investigation, during orthodontic tooth movement, temporary increment of the viscoelastic property values coincidentally occurred with the temporary stop period of the tooth movement, and the relationship between the viscoelastic property changes and the tooth movement was strongly suggested.The results of this project suggest that the investigations about the viscoelastic property changes of the periodontal tissue could indicate the conditions of the periodontal tissue. It also suggested that this method had the possibility to be the clinically efficient index to determine the periodontal tissue conditions during the orthodontic tooth movement. Less